SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
This powerpoint presents a sparse transmitarray design for 6G technology. The proposed approach leverages aperiodic arrays with large inter-element spacings, offering grating lobe-free operation, enhanced gain, and narrow beamwidths. The transmitarray topology, designed for sub-THz and THz frequencies, simplifies feed-network complexity, and minimizes losses. Numerical analysis and full wave simulation results show this approach is feasible.
NASA is embarked upon research and development tasks aimed at providing the general aviation industry with a reliable crashworthy airframe design technology. The goals of the NASA program are: reliable analytical techniques for predicting the nonlinear behavior of structures; significant design improvements of airframes; and simulated full-scale crash test data. The analytical tools will include both simplified procedures for estimating energy absorption characteristics and more complex computer programs for analysis of general airframe structures under crash loading conditions. The analytical techniques being developed both in-house and under contract are described, and a comparison of some analytical predictions with experimental results is shown.
The collisional processes which transfer momentum between counterstreaming plasmas are reviewed and applied to the example of a laser-produced plasma expanding into a partially ionized background. Experimental measurements of the dependence of the ion flow field on collisional momentum transfer demonstrate the validity of the simplified treatment of collision processes which have been adopted. A numerical model which simulates the laser-plasma interaction with the background confirms the importance of collisions in previous experimental studies of momentum coupling, and provides some insight into the distinction between collisional and collisionless flow regimes.
Azimuth correlation simulates large antenna aperature. It uses charge-coupled-device (CCD) technology to simplify complex, digital, signal-improvement process. In aircraft or spacecraft, correlator processes images onboard and in real time to simplify transmission to ground stations.
An experimental and analytical investigation was conducted to determine the effect of a ceramic coating on the average metal temperatures of full annular, film cooled combustion chamber liner. The investigation was conducted at pressures from 0.50 to 0.062. At all test conditions, experimental results indicate that application of a ceramic coating will result in significantly lower wall temperatures. In a simplified heat transfer analysis, agreement between experimental and calculated liner temperatures was achieved. Simulated spalling of a small portion of the ceramic coating resulted in only small increases in liner temperature because of the thermal conduction of heat from the hotter, uncoated liner metal.
Temperatures recorded during two KOSI comet nucleus simulation experiments strongly suggest that heat transport by vapor flow into the interior of the sample is very important. Two comet nucleus simulation experiments have been done by the KOSI team in a big space simulator. The thermal evolution of the sample during insolation and the results of simplified thermal evolution calculations are discussed. The observed thermal histories cannot be explained by a simple model with heat transferred by heat conduction at a constant conductivity, so a coupled heat and mass transfer problem was considered. The porous ice matrix was assumed to have a constant thermal conductivity and to be in thermal equilibrium with vapor in the pores, the internal pressure being the vapor pressure. The vapor was modelled as an ideal gas because, at the temperatures relevant to the problem, the mean free path length of the vapor molecules is large in comparison with the pore dimensions. The heat capacity at constant volume per unit mass of the two phase mixture was also assumed constant. The vapor was allowed to flow and transfer heat in response to an internal pressure gradient.
The transport of dust in the Martian atmosphere into high northern latitudes as a result of a Martian polar-warming (and global-dust-storm) event was investigated using a simplified transport model in conjunction with a beta-plane dynamical model to simulate the transport of dust. Numerical experiments were performed to examine the influence of different warming dynamics and to assess the sensitivity of the transport to the initial dust distribution. Results indicate that substantial amounts of dust could be transported and deposited at high northern latitudes (extending to the pole) in a polar-warming event. The potential for the transport of water was also examined through simulations, with results indicating that large amounts of water could be transported to the north polar region in a warming, on the condition that substantial condensation and precipitation do not take place in the subpolar regions. However, the warmth of the Martian atmosphere during global dust storms makes the latter possible.
A new disturbance-adaptive control strategy for multiple pointing-mount space platforms is proposed and illustrated by consideration of a simplified 3-link dynamic model of a multiple pointing-mount space platform. Simulation results demonstrate the effectiveness of the new platform control strategy. The simulation results also reveal a system 'destabilization phenomena' that can occur if the set of individual platform-mounted experiment controllers are 'too responsive.'
During phase 2 research on the application of active noise control to jet engines, the development of multiple-input/multiple-output (MIMO) active adaptive noise control algorithms and acoustic/controls models for turbofan engines were considered. Specific goals for this research phase included: (1) implementation of a MIMO adaptive minimum variance active noise controller; and (2) turbofan engine model development. A minimum variance control law for adaptive active noise control has been developed, simulated, and implemented for single-input/single-output (SISO) systems. Since acoustic systems tend to be distributed, multiple sensors, and actuators are more appropriate. As such, the SISO minimum variance controller was extended to the MIMO case. Simulation and experimental results are presented. A state-space model of a simplified gas turbine engine is developed using the bond graph technique. The model retains important system behavior, yet is of low enough order to be useful for controller design. Expansion of the model to include multiple stages and spools is also discussed.
An improved version of the Wall Signature Method was developed to compute wall interference effects in three-dimensional subsonic wind tunnel testing of aircraft models in real-time. The method may be applied to a full-span or a semispan model. A simplified singularity representation of the aircraft model is used. Fuselage, support system, propulsion simulator, and separation wake volume blockage effects are represented by point sources and sinks. Lifting effects are represented by semi-infinite line doublets. The singularity representation of the test article is combined with the measurement of wind tunnel test reference conditions, wall pressure, lift force, thrust force, pitching moment, rolling moment, and pre-computed solutions of the subsonic potential equation to determine first order wall interference corrections. Second order wall interference corrections for pitching and rolling moment coefficient are also determined. A new procedure is presented that estimates a rolling moment coefficient correction for wings with non-symmetric lift distribution. Experimental data obtained during the calibration of the Ames Bipod model support system and during tests of two semispan models mounted on an image plane in the NASA Ames 12 ft. Pressure Wind Tunnel are used to demonstrate the application of the wall interference correction method.
Experiments on a scale model of an advanced unconventional subsonic transport concept, the Blended Wing Body (BWB), have demonstrated significant shielding of inlet-radiated noise. A computational model of the shielding mechanism has been developed using a combination of boundary integral equation method (BIEM) and equivalent source method (ESM). The computation models the incident sound from a point source in a nacelle and determines the scattered sound field. In this way the sound fields with and without the airfoil can be estimated for comparison to experiment. An experimental test bed using a simplified wedge-shape airfoil and a broadband point noise source in a simulated nacelle has been developed for the purposes of verifying the analytical model and also to study the effect of engine nacelle placement on shielding. The experimental study is conducted in the Anechoic Noise Research Facility at NASA Langley Research Center. The analytic and experimental results are compared at 6300 and 8000 Hz. These frequencies correspond to approximately 150 Hz on the full scale aircraft. Comparison between the experimental and analytic results is quite good, not only for the noise scattering by the airframe, but also for the total sound pressure in the far field. Many of the details of the sound field that the analytic model predicts are seen or indicated in the experiment, within the spatial resolution limitations of the experiment. Changing nacelle location produces comparable changes in noise shielding contours evaluated analytically and experimentally. Future work in the project will be enhancement of the analytic model to extend the analysis to higher frequencies corresponding to the blade passage frequency of the high bypass ratio ducted fan engines that are expected to power the BWB.
Experiments on a scale model of an advanced unconventional subsonic transport concept, the Blended Wing Body (BWB), have demonstrated significant shielding of inlet-radiated noise. A computational model of the shielding mechanism has been developed using a combination of boundary integral equation method (BIEM) and equivalent source method (ESM). The computation models the incident sound from a point source in a nacelle and determines the scattered sound field. In this way the sound fields with and without the airfoil can be estimated for comparison to experiment. An experimental test bed using a simplified wedge-shape airfoil and a broadband point noise source in a simulated nacelle has been developed for the purposes of verifying the analytical model and also to study the effect of engine nacelle placement on shielding. The experimental study is conducted in the Anechoic Noise Research Facility at NASA Langley Research Center. The analytic and experimental results are compared at 6300 and 8000 Hz. These frequencies correspond to approximately 150 Hz on the full scale aircraft. Comparison between the experimental and analytic results is quite good, not only for the noise scattering by the airframe, but also for the total sound pressure in the far field. Many of the details of the sound field that the analytic model predicts are seen or indicated in the experiment, within the spatial resolution limitations of the experiment. Changing nacelle location produces comparable changes in noise shielding contours evaluated analytically and experimentally. Future work in the project will be enhancement of the analytic model to extend the analysis to higher frequencies corresponding to the blade passage frequency of the high bypass ratio ducted fan engines that are expected to power the BWB.
The Lunar Surface System Habitat Demonstration Unit (HDU) will require a project team to integrate a variety of contributions from National Aeronautics and Space Administration (NASA) centers and potential outside collaborators and poses a challenge in integrating these disparate efforts into a cohesive architecture. To accomplish the development of the first version of the HDU, the Pressurized Excursion Module (PEM), from conception in June 2009 to rollout for operations in July 2010, the HDU project team is using several strategies to mitigate risks and bring the separate efforts together. First, a set of design standards is being developed to define the interfaces between the various systems of PEM and to the payloads, such as the Geology Laboratory, that those systems will support. Scheduled activities such as early fit-checks and the utilization of a habitat avionics test bed prior to equipment installation into HDU PEM are planned to facilitate the integration process. A coordinated effort to establish simplified Computer Aided Design (CAD) standards and the utilization of a modeling and simulation systems will aid in design and integration concept development. Finally, decision processes on the shell development including the assembly sequence and the transportation have been fleshed out early on HDU design to maximize the efficiency of both integration and field operations.
The impact of aircraft emissions and contrails on the environment adds an additional aspect to aircraft trajectory optimization. This study developed a three-dimensional trajectory optimization algorithm for trans-Atlantic flights in cruise to generate aircraft trajectories that minimize environmental impacts due to CO2 emissions and contrails in the presence of winds. The climate-optimal trajectory is developed using dynamic programming that adjusts a wind-optimal aircraft heading while determining the optimal locations, altitudes and times for en-route step climbs. Flying wind-optimal routes minimize aircraft travel time, fuel burn and associated emissions during cruise while adjusting aircraft heading and en-route step climbs at the optimal locations and times minimize climate impact of contrails. This capability integrates an air traffic management simulation with aircraft fuel burn and emissions models, contrail formation and dispersion models, simplified climate response models, and a common climate metric. A study was conducted to evaluate the potential cost and benefits of flying climate-optimal routes in North Atlantic Airspace and their impacts to the Organized Track System design based on the trans-Atlantic air traffic during a day, July 12, 2012. Results show eastbound flights achieved a larger environmental benefit with less additional fuel burn than westbound flights that operated in strong headwinds that caused more additional fuel burn and aircraft emissions to avoid traversing contrails favorable regions.
Accurate numerical modeling of clouds and precipitation is essential for weather forecasting and climate change research. While size-resolved (bin) cloud microphysics models predict particle size distributions without imposing shapes, results are subject to artificial size distribution broadening owing to numerical diffusion associated with various processes. Whereas Part 1 addressed collision-coalescence, here we investigate numerical diffusion that occurs in solving condensation and evaporation. In a parcel model framework, all of the numerical schemes examined converge to one solution of condensation and evaporation as the mass grid is refined, and the advection-based schemes are recommended over the reassigning schemes. Including Eulerian vertical advection in a column limits the convergence to some extent, but that limitation occurs at a sufficiently fine mass grid, and the number of iterations in solving vertical advection should be minimized to reduce numerical diffusion. Insubstantial numerical diffusion in solving condensation can be amplified if collision-coalescence is also active, which in turn can be substantially diminished if turbulence effects on collision are incorporated. Large-eddy simulations of a drizzling stratocumulus field reveal that changes in moments of Doppler spectra obtained using different mass grids are consistent with those obtained from the simplified framework, and that spectral moments obtained using a mass grid designed to effectively reduce numerical diffusion are generally closer to observations. Notable differences between the simulations and observations still exist, and our results suggest a need to consider whether factors other than numerical diffusion in the fundamental process schemes employed can cause such differences.
The Gateway is an upcoming long term lunar exploration program to be completed by NASA in partnership with ESA and other US and international partners. The system design of the Gateway contains both a high performance Xenon based Solar Electric Propulsion system, as well as a bi-propellant attitude control system. Both propulsion systems are designed for on-orbit refueling to enable long life performance of the Gateway. The ESPRIT-RM is a module which will expand the pressurized volume of Gateway, while also providing refueling capability for both the Xenon and Bipropellant propulsion systems, therefore extending the Gateway life on orbit. As part of the Gateway bi-propellant refueling system development, a simplified fluidic breadboard system was created to evaluate system performance and response using simulant fluids. The test plan includes verification activities with simulant (water, HFE-7100) to verify joined subsystem behavior in the critical operations, including propellant transfer demonstration between modules, transient tests and venting tests. Integrated testing occurred at TASUK in collaboration with NASA to support joint verification activities to de-risk the major functions of the ESPRIT BTS and the overall CONOPS of the refueling of the Gateway chemical propulsion system. Initially collected test data from the system testing is presented, as well as initial model validation, and correlated to collected high frequency test data and system response is shown. Initially collected data has shown the architected system performance is closing initial design assumptions, but much forward work remains to characterize and develop the system.
The Gateway is an upcoming long term lunar exploration program to be completed by NASA in partnership with ESA and other US and international partners. The system design of the Gateway contains both a high performance Xenon based Solar Electric Propulsion system, as well as a bi-propellant attitude control system. Both propulsion systems are designed for on-orbit refuelling to enable long life performance of the Gateway. The ESPRIT-RM is a module which will expand the pressurized volume of Gateway, while also providing refuelling capability for both the Xenon and Bipropellant propulsion systems, therefore extending the Gateway life on orbit. As part of the Gateway bi-propellant refuelling system development, a simplified fluidic breadboard system was created to evaluate system performance and response using simulant fluids. The test plan includes verification activities with simulant (water, HFE-7100) to verify joined subsystem behaviour in the critical operations, including propellant transfer demonstration between modules, transient tests and venting tests. Integrated testing will occur at TASUK in collaboration with NASA to support joint verification activities to de-risk the major functions of the ESPRIT Bipropellant Transfer Subsystem (BTS) and the overall CONOPS of the refuelling of the Gateway chemical propulsion system. Initially collected test data is presented and has shown the architected system performance is closing initial design assumptions, but much forward work is identified to continue to characterize and develop the system.
Direct numerical simulation and pore-network modeling are common approaches to study the physics of two-phase flow through natural rocks. For assessment of the long-term performance of geological sequestration of CO 2 , it is important to model the full drainage-imbibition cycle to provide an accurate estimate of the trapped CO 2 . While direct numerical simulation using pore geometry from micro-CT rock images accurately models two-phase flow physics, it is computationally prohibitive for large rock volumes. On the other hand, pore-network modeling on networks extracted from micro-CT rock images is computationally efficient but utilizes simplified physics in idealized geometric pore elements. This study uses the lattice-Boltzmann method for direct numerical simulation of CO 2 -brine flow in idealized pore elements to develop a new set of pore-level flow models for the pore-body filling and snap-off events in pore-network modeling of imbibition. Lattice-Boltzmann simulations are conducted on typical idealized pore-network configurations, and the interface evolution and local capillary pressure are evaluated to develop modified equations of local threshold capillary pressure of pore elements as a function of shape factor and other geometrical parameters. The modified equations are then incorporated into a quasi-static pore-network flow solver. The modified model is applied on extracted pore-network of sandstone samples, and saturation of residual trapped CO 2 is computed for a drainage-imbibition cycle. The modified model yields different statistics of pore-level events compared with the original model; in particular, the occurrence of snap-off in pore-throats is reduced resulting in a more frontal displacement pattern along the main injection direction. Compared to the original model, the modified model is in closer agreement with the residual trapped CO 2 obtained from core flow experiments and direct numerical simulation.